Thermoelectric generating device



Feb. 25, 1947. w RAY THERMOELECTRIC GENERATING DEVICE Filed May 1, 1944hJulaZzTa/z 2 3noentor: WILL/AM A. PA Y,

Psamd Feb. 25, 1941 THERMOELECTRIC GENERATING DEVICE William A. Ray, LosAngeles, Calif., or to General Controls 00., acorporation ApplicationMay 1, 1944, Serial No. 533,511

4 Claims.

September 12, 1941; now Patent No. 2,349,306,

granted May 23, 1944.

Devices of the type indicated are commonly employed for the control ofgas-buming systems, the device usually being so arranged as to be heatedby the flame of a pilot burner provided for the ignition of the mainburner of the system, so that the device serves not only as a convenientsource oi electrical energy independent of the utility service, but alsoas safety means which, due to the resultant cessation of generation,acts to render the system inoperative upon accidental extinguishment ofthe pilot burner flame.

When the device is heated by a gas flame, the dissimilar metals of whichits elements are composed are subject not only to oxidation but also tothe corrosive action of theburnt or unburnt gases. It has been proposedin the prior art to provide a shield or cap of stainless steel for eachof the hot junctions of the device to protect them from the directaction of the flame; however, such means have been found to beinadequate, particularly whenhigh direct and/or ambient temperatures areinvolved, because of the penetration of the gases beneath the shield. Itis therefore an object of my invention to provide means for hermeticallysealing the heated portions of the thermocouple elements from theatmosphere and other gases, without materially reducing transfer of heatto the hot junctions.

Another object is to provide a thermoelectric generating devicecomprising a metallic container for a thermopile, which containerprovides means for maintaining the hot-junction portions of thethermopile in good heat-transfer relation to a portion of the containeradapted to be subjected to a source of heat.

Other objects and advantages of the invention will be. found in thedescription, the drawing, and the claims; and, for full understanding ofthe invention, reference may be had to the following detaileddescription and accompanying drawing, wherein:

Figure 1 is a longitudinal sectional view of a thermoelectric generatingdevice embodying the invention; and

Figure 2 is an enlarged transverse section taken along the line 22 ofFig. 1.

In the drawing, the numeral I l indicates a cylindrical tubular member,or housing, of relatively thin sheet metal. The upper end'of this memberis closed and provided in its end wall with a deep central depression I!which forms with the side wall of the member an internal annular recessl3 (Fig. 2) for reception of the twisted hot-junction end portions of athermopile. This thermopile comprises agenerallycircumferentially-arranged group of pairs (six pairs, as shown) ofthermocouple elements or wires i5 joined together in electrical series.

As is seen in Fig. 2, the individual wires of the thermopile arethreaded through a circular row of holes It in a disk ll, of ceramicmaterial such as porcelain, and are twisted together at opposite sidesof the disk to form the upper hot-junction portions [4 and cold-junctionportions l8; the junctions themselves being at the points of firstcontact of the elements, as indicated at M and I8 for the respective hotand cold junctions. It will be understood that the terms hot and "coldare herein employed merely as a convenient way of indicating theopposite junctions of a thermocouple; the hot junction being the onewhich is to be subjected to heat or cold, while the cold junction is theone subjected to ambient temperature. The materials of the thermocoupleelements may be selected from any of the wellknown metals or alloyshaving highly different ChromeP and Copel.

thermoelectric powers, such as, for example,

To avoid possible confusion, the back pairs of elements are not shown inFig. 1, nor are the end elements of the thermopile whereby it isconnected in an electrical circult; it being believed that thearrangement of the thermopile will be apparent to those skilled in theart. The general structure or the present device is the same as thatdisclosed in my Patent No. 2,349,306 referred to above.

The active portions of the thermocouple elements between their hot andcold junctions (i. e., between the points of first contact oftheelements at opposite sides of disk l'|-) are preferably quite short, asshown, so that the electrical resistance of the thermopile will not beexcessive when it isconstructed of materials having high resistivity,such as the alloys mentioned. In order to maintain the cold junctionsrelatively cool despite their proximity to the hot junctions, each ofthe coldjunctio'n portions i8 is attached to a tube IQ, of metal, suchas copper, having high thermal conductivity, which extends throughopenings in insulating disks.20 and 21 to the lower end of the tubularmember II where the temperature is always relatively low since only theextreme upper end portion or tip of the tubular member is intended to besubjected to the flame or other source of heat. This heat-dissipatingfeature is covered in the copending application of William R. Ray,

Serial No. 265,974, filed April 4, 1939; now Patent No. 2,374,701,granted May 1, 1945.

Sealingly closing the bottom end oi. the tubular member II is a basefitting 22 wherein are provided contact elements or prongs 23 adapted tocooperate with an electrical socket (not shown) of the .type employedfor mounting conventional vacuum tubes. Sealing of the contact elementsin the base fitting 22 may be accomplished in any convenient manner: forexample, if the base is of molded insulating material, the material canbe molded around the contact prongs; or it it is of metal, the prongs orthe leads can be mounted in glass beads as in metal radio tubes. Theinnet ends of the prongs 23 are connected to copper tubes 24 which inturn are connected to the end elements (mentioned above) of thethermopile. A rod 25 maintains the disks ll, 20 and 2| in relation toeach other and to the tubular memher, and thereby holds the hot-junctionportions M of the thermopile within the recess l3. Thin wrappings 26(shown of exaggerated thickness in the drawing) of mica or othersuitable material are employed .to electrically insulate the hotjunctionportions from the tubular member, the

recess 13 having a width such as to tightly receive the insulatedhot-junction portions. The rod 25 extends from the base 22 throughcentral openings in the disks ll, 20 and 2| and is pinchedout at theiropposite sides to provide the required support.

The interior of the device may be evacuated, or, preferably, filled withan inert gas, such as nitrogen, to aid conduction of heat away from thecold-junction portions l8 and their extensions IS.

The embodiment of my invention herein shown and described is obviouslysusceptible of modiflcatlon without departing from the spirit of theinvention, and I intend therefore to be limited only by the scope of theappended claims.

I claim as my invention: v

1. A thermoelectric generating device adapted to be subjected to asource of heat and comprising, in combination: an elongated tubularmember closed at one end and formed of relatively thin sheet metal, athermopile within said tubular member and comprising a plurality ofpairs of elongated thermocouple elements arranged in substantiallyparallel axial relation to each other and to the member and forming attheir opposite ends a plurality of hot and of cold junctions, saidclosed end of the tubular member being centrally depressed to forminternally an annular recess for so closely receiving the hot-junctionportions of said thermocouple elements that they are maintained in goodheat-transfer relation to said end of the member, and means forelectrically insulating said hot-junction portions from the member.

2. A thermoelectric generating device adapted tube subjected to a sourceof heat and comprising, in combination: an elongated tubular memberclosed at one end and formed of relatively thin sheet metal, athermopile within said tubular member and comprising a plurality ofpairs of elongated thermocouple elements arranged in substantiallyparallel axial relation to each other and to the member and forming attheir opposite ends a plurality of hot and of cold junctions, said oneend of the tubular member being centrally depressed to form internallyan annular recess for so closely receiving the hot-junction portions ofsaid thermocouple elements that they are maintained in goodheat-transfer relation to said one end of the member, means forelectrically insulating said hot-junction portions from the member, anda base-fitting closing the opposite end of the tubular member and havingcontact elements for connecting the thermopile in an external electricalcircuit.

3. A thermoelectric generating device adapted to be subjected to asource of heat and comprising, in combination: an elongated tubular.member closed at one end and formed of relatively thin sheetmetal, athermopile within said tubular member and comprising a plurality ofpairs of elongated thermocouple elements arranged in substantiallyparallel axial relation to each other and to the memberand forming attheir opposite ends a plurality of hot'and of cold junctions,heat-conducting means joined to and extending from each of said hotjunctions generally axially of the elements, said one end of the memberbeing centrally depressed to form internally a deep annular recess forso closely receiving said heat-conducting means that they are maintainedin good heat-transfer relation to said one end of the member, and meansfor electrically insulating said heat-conducting means from the member.

4. A thermoelectric generating device, as defined in claim 3, includinga base-fitting for closing the opposite end of the tubular member and.

having contact elements for connecting the thermopile in an externalelectrical circuit.

WILLIAM A. RAY.

REFERENCES CITED The following references are of record in the file ofthis. patent:

UNITED STATES PATENTS OTHER REFERENCES Patton et al., Ind. and Eng.Chem., anal, ed.,

vol. 13, 1941, pages 823, 824. (Copy in Div. 59.)

